Klovera,
Here's the best steps for debugging the issue. From what you've described, we can't recreate the problem. Hopefully the below will help to spit out an error that will let us determine the exact cause:
1) Turn of GZip compression. This is a setting in the Joomla Global Config area, but sometimes can also be enabled in your template as well as minification plugins.
2) Turn error reporting to Maximum (also in Global Configurations)
3) Enable just one plugin (Kunena or JomSocial). Disable all settings in the Profiles area (always import, import avatar), etc.
4) Test to see if you still get the error.
** If so, hopefully there's a better message now.
** If not, start enabling some of the options in the Profile area until you get the error. If no error appears, disabling that profile plugin and enable the other one. Step through options and see what happens.
Would love to get you to the bottom of this!
Alex
JFBConnect - Profiles - JomSocial
